(function () {

    var C = (typeof window === 'undefined') ? require('./Crypto').Crypto : window.Crypto;

// Shortcuts
    var util = C.util,
        charenc = C.charenc,
        UTF8 = charenc.UTF8,
        Binary = charenc.Binary;

// Constants
    var K = [0x428A2F98, 0x71374491, 0xB5C0FBCF, 0xE9B5DBA5,
        0x3956C25B, 0x59F111F1, 0x923F82A4, 0xAB1C5ED5,
        0xD807AA98, 0x12835B01, 0x243185BE, 0x550C7DC3,
        0x72BE5D74, 0x80DEB1FE, 0x9BDC06A7, 0xC19BF174,
        0xE49B69C1, 0xEFBE4786, 0x0FC19DC6, 0x240CA1CC,
        0x2DE92C6F, 0x4A7484AA, 0x5CB0A9DC, 0x76F988DA,
        0x983E5152, 0xA831C66D, 0xB00327C8, 0xBF597FC7,
        0xC6E00BF3, 0xD5A79147, 0x06CA6351, 0x14292967,
        0x27B70A85, 0x2E1B2138, 0x4D2C6DFC, 0x53380D13,
        0x650A7354, 0x766A0ABB, 0x81C2C92E, 0x92722C85,
        0xA2BFE8A1, 0xA81A664B, 0xC24B8B70, 0xC76C51A3,
        0xD192E819, 0xD6990624, 0xF40E3585, 0x106AA070,
        0x19A4C116, 0x1E376C08, 0x2748774C, 0x34B0BCB5,
        0x391C0CB3, 0x4ED8AA4A, 0x5B9CCA4F, 0x682E6FF3,
        0x748F82EE, 0x78A5636F, 0x84C87814, 0x8CC70208,
        0x90BEFFFA, 0xA4506CEB, 0xBEF9A3F7, 0xC67178F2];

// Public API
    var SHA256 = C.SHA256 = function (message, options) {
        var digestbytes = util.wordsToBytes(SHA256._sha256(message));
        return options && options.asBytes ? digestbytes :
            options && options.asString ? Binary.bytesToString(digestbytes) :
                util.bytesToHex(digestbytes);
    };

// The core
    SHA256._sha256 = function (message) {

        // Convert to byte array
        if (message.constructor == String) message = UTF8.stringToBytes(message);
        /* else, assume byte array already */

        var m = util.bytesToWords(message),
            l = message.length * 8,
            H = [0x6A09E667, 0xBB67AE85, 0x3C6EF372, 0xA54FF53A,
                0x510E527F, 0x9B05688C, 0x1F83D9AB, 0x5BE0CD19],
            w = [],
            a, b, c, d, e, f, g, h, i, j,
            t1, t2;

        // Padding
        m[l >> 5] |= 0x80 << (24 - l % 32);
        m[((l + 64 >> 9) << 4) + 15] = l;

        for (var i = 0; i < m.length; i += 16) {

            a = H[0];
            b = H[1];
            c = H[2];
            d = H[3];
            e = H[4];
            f = H[5];
            g = H[6];
            h = H[7];

            for (var j = 0; j < 64; j++) {

                if (j < 16) w[j] = m[j + i];
                else {

                    var gamma0x = w[j - 15],
                        gamma1x = w[j - 2],
                        gamma0 = ((gamma0x << 25) | (gamma0x >>> 7)) ^
                            ((gamma0x << 14) | (gamma0x >>> 18)) ^
                            (gamma0x >>> 3),
                        gamma1 = ((gamma1x << 15) | (gamma1x >>> 17)) ^
                            ((gamma1x << 13) | (gamma1x >>> 19)) ^
                            (gamma1x >>> 10);

                    w[j] = gamma0 + (w[j - 7] >>> 0) +
                        gamma1 + (w[j - 16] >>> 0);

                }

                var ch = e & f ^ ~e & g,
                    maj = a & b ^ a & c ^ b & c,
                    sigma0 = ((a << 30) | (a >>> 2)) ^
                        ((a << 19) | (a >>> 13)) ^
                        ((a << 10) | (a >>> 22)),
                    sigma1 = ((e << 26) | (e >>> 6)) ^
                        ((e << 21) | (e >>> 11)) ^
                        ((e << 7) | (e >>> 25));


                t1 = (h >>> 0) + sigma1 + ch + (K[j]) + (w[j] >>> 0);
                t2 = sigma0 + maj;

                h = g;
                g = f;
                f = e;
                e = (d + t1) >>> 0;
                d = c;
                c = b;
                b = a;
                a = (t1 + t2) >>> 0;

            }

            H[0] += a;
            H[1] += b;
            H[2] += c;
            H[3] += d;
            H[4] += e;
            H[5] += f;
            H[6] += g;
            H[7] += h;

        }

        return H;

    };

// Package private blocksize
    SHA256._blocksize = 16;

    SHA256._digestsize = 32;

})();
